<!DOCTYPE htmml>
<html lang="en">
<head>
    <meta charset="UTF-8"/>
	<title>伪类</title>
	<style>
	.wrap div{
	    background-color:red;
		float:left;
		width:300px;
		height:50px;
	}
	.wrap:after{
		content:"";
	    display:block;
		clear:both;
	}
	.bg{
	    background-color:blue;
	}
	</style>
</head>
<body>
    <div class="wrap">伪类1
	    <div>伪类2</div>
<!--伪类清除浮动的方法after  主流方式-->
	</div>
	<div class="bg">实创网络协会</div>
</body>
</html>